Harvey B J, Ehrenfeld J
Département de Biologie, Laboratoire Jean Maetz, Villefranche-sur-Mer, France.
J Gen Physiol. 1988 Dec;92(6):793-810. doi: 10.1085/jgp.92.6.793.
Ion-sensitive microelectrodes and current-voltage analysis were used to study intracellular pH (pHi) regulation and its effects on ionic conductances in the isolated epithelium of frog skin. We show that pHi recovery after an acid load is dependent on the operation of an amiloride-sensitive Na+/H+ exchanger localized at the basolateral cell membranes. The antiporter is not quiescent at physiological pHi (7.1-7.4) and, thus, contributes to the maintenance of steady state pHi. Moreover, intracellular sodium ion activity is also controlled in part by Na+ uptake via the exchanger. Intracellular acidification decreased transepithelial Na+ transport rate, apical Na+ permeability (PNa) and Na+ and K+ conductances. The recovery of these transport parameters after the removal of the acid load was found to be dependent on pHi regulation via Na+/H+ exchange. Conversely, variations in Na+ transport were accompanied by changes in pHi. Inhibition of Na+/K+ ATPase by ouabain produced covariant decreases in pHi and PNa, whereas increases in Na+ transport, occurring spontaneously or after aldosterone treatment, were highly correlated with intracellular alkalinization. We conclude that cytoplasmic H+ activity is regulated by a basolateral Na+/H+ exchanger and that transcellular coupling of ion flows at opposing cell membranes can be modulated by the pHi-regulating mechanism.
利用离子敏感微电极和电流-电压分析技术，研究了蛙皮离体上皮细胞内pH值（pHi）的调节及其对离子电导的影响。我们发现，酸负荷后pHi的恢复依赖于位于基底外侧细胞膜上的氨氯地平敏感型Na⁺/H⁺交换体的运作。在生理pHi（7.1 - 7.4）时，该反向转运体并非静止不动，因此有助于维持pHi的稳态。此外，细胞内钠离子活性也部分受通过该交换体的Na⁺摄取的控制。细胞内酸化降低了跨上皮Na⁺转运速率、顶端Na⁺通透性（PNa）以及Na⁺和K⁺电导。发现去除酸负荷后这些转运参数的恢复依赖于通过Na⁺/H⁺交换进行的pHi调节。相反，Na⁺转运的变化伴随着pHi的改变。哇巴因抑制Na⁺/K⁺ ATP酶导致pHi和PNa协同降低，而自发出现或醛固酮处理后Na⁺转运的增加与细胞内碱化高度相关。我们得出结论，细胞质H⁺活性由基底外侧Na⁺/H⁺交换体调节，并且在相对细胞膜处离子流的跨细胞偶联可由pHi调节机制进行调控。
